Purdue News

September 4, 2002

Forages need TLC, rest after rough summer, specialist says

WEST LAFAYETTE, Ind.  Forage crops have taken a beating this summer from drought, heat, livestock traffic, insects and weeds. This fall, farmers might want to give their pastures some tender loving care  and a little rest, too.

Producers should inspect their forage stands to determine the health of the crop, said Keith Johnson, Purdue University Cooperative Extension Service forage specialist. If problems exist, soil fertility testing might be necessary and appropriate fertilizers applied. Reseeding damaged pastures, controlling weeds and establishing a rotational grazing system also will help rejuvenate puny pastures, he said.

Given the environmental conditions working against forages this year, it's amazing producers were able to raise a crop at all.

"This was one of the more stressful seasons for forages," Johnson said.

Excessive spring rains produced good hay yields but made it nearly impossible for farmers to harvest the crop.

"The problem was really twofold," Johnson said. "No. 1, with hay we couldn't be timely with our harvest. Second, when we were grazing livestock, some pretty extreme damage was done to fields by the hoof action of the animals. Then, dry weather set in. As we got into August, we saw that this dry weather was slowing alfalfa growth. And potato leafhopper, which is an insect that causes damage to alfalfa, was starting to cause some negative effects on yield as well."

Throw in an infestation of alfalfa weevil, another forage pest, and hearty weed populations, and pastures and hay fields quickly went downhill.

1. Assess the forage stand  Tour pasture and identify the plants that are present. If unsure whether a plant is a forage or weed, refer to the Purdue Forage Identification Web site.

2. Address soil fertility problems  "Soil fertility issues ought to be resolved," Johnson said. "If we have low phosphorus, potassium, pH concerns  those are things that we have some control over to alleviate stresses, inefficiencies or weak stands. If we haven't done so we need to be soil testing, and then follow through with appropriate amendments of fertilizer and limestone."

3. Strengthen weak stands by reseeding pastures  "The base pasture in Indiana ought to be a productive cool-season grass and legume that's adapted to the site," Johnson said. "As a producer walks a pasture he needs to assess what is really there, whether it's a productive legume and grass. The legume ought to be contributing somewhere in the neighborhood of 30 percent of the stand, which is roughly the equivalent of two plants per square foot of legume. A productive pasture's going to have 90 percent or greater cover of land surface, so there should not be a lot of bare soil."

Johnson advises against mixing cool-season grasses and legumes in a broadcaster, combining red clover and alfalfa seed, and overseeding an alfalfa field with alfalfa.

"We need to provide some rest for forages, which is critical for longevity of stand and its vigor and health," Johnson said. "So as one thinks about the future, we need to consider incorporating some form of rotation system to provide that rest.

"In terms of getting a rotational grazing program going, that ought to be thought about in the fall and winter, and then begin implementation by breaking the pasture into paddocks at the first opportunity in the late winter and springtime."

5. Control winter annual weeds  Choose a herbicide best suited to knock out problem weeds in your alfalfa fields. Most herbicides should be applied after the alfalfa is dormant in the autumn and before dormancy breaks in the spring.

6. Treat pastures damaged by alfalfa weevil and potato leafhopper  "If economic thresholds are reached, then these pests should be controlled with an insecticide, or harvest alfalfa if it is past the late bud stage of plant development," Johnson said.

Field trials at the Purdue Agronomy Research Center indicate a failure to control high potato leafhopper populations during a seeding year can reduce yields of both susceptible and potato leafhopper-resistant alfalfa varieties the following year.